1. Field of the Invention
The present invention relates to a novel succinimide derivative, a process for producing the same and an application of the same in the field of resist.
2. Background Information
In recent years, quarter-micron pattern formations have been demanded with the increase of the integration level of semi-conductive integral circuits. Particularly, the eximer laser lithography using krypton fluoride (KrF) or argon fluoride (ArF) as the light source has attracted attention because it enables production of 64 MDRAM and 256 MDRAM. Conventionally, near-ultraviolet rays have mainly been used in the lithography process. As the light source has been changed, however, the following properties have newly been required in addition to the conventionally required properties such as heat resistance, ratio of residual film thickness after developing (film retention ratio), profile and others
a) high photospeed to KrF and ArF eximer laser light source, and PA1 b) high resolution.
Under these circumstances, has been proposed a type of resist, generally called chemical amplification type resist, which utilizes a chemical amplification effect of an acid-catalyst. In the chemical amplification type resist, the solubility of exposed part in an alkaline developing solution is realized by a reaction catalyzed by an acid which is generated from an acid generating agent by irradiation of radial rays and this affords a positive resist.
Conventionally, for the production of the chemical amplification type positive resist, polyvinylphenols in which the phenolic hydroxyls are protected by groups removable by the action of an acid have been used. The resist utilizing these resins has a defect that it is generally liable to be affected by its environment. Particularly, in the step of effecting the elimination reaction of the protective groups by heat treatment after exposure to rays (Post Exposure Bake; hereinafter, abbreviated as PEB), it is known that properties are greatly varied according to the period of standing before the heat treatment. This phenomenon is sometimes called Time Delay effect, and it may cause deterioration, of the resolution, T-top forming (T-shaping) in the pattern after development and bad repeatability of critical dimension.
It is considered that the reason for such a phenomenon is due to deactivation of the generated acid caused by basic substances such as ammonia and N-methylpyrrolidone which exist in an ambient atmosphere where the lithography is conducted and come into contact with the coating film. It is known, for example, that even if the content of ammonia in the air is as low as about 20 ppb, a pattern obtained by PEB carried out 30 minutes after exposure has a profile with remarkable T-shaping.
There is also a problem that, in the production of a quarter micron pattern, inferior etching caused by lying or peeling off of a smaller pattern is liable to occur.
An object of the present invention is to provide a novel compound which exerts excellent effects when used as an acid generating agent for a resist composition comprising an alkali-soluble resin having protective groups removable by the action of an acid.
Another object of the invention is to provide a resist composition, using such compound, which is excellent in photospeed and resolution and which is improved in the time delay effect and adhesion of pattern, while keeping heat resistance, ratio of residual film thickness after developing, uniformity of film thickness, profile and so on at high levels.
After extensive studies, the present inventors have successfully found a novel succinimide compound and discovered the fact that a resist composition comprising the compound together with an alkali-soluble resin having protective groups removable by the action of an acid is excellent in photospeed and resolution and improved in the time delay effect and adhesion of the pattern, while keeping heat resistance, ratio of residual film thickness after developing, uniformity of film thickness, profile and so on at high levels. Thus, the present invention has been completed.